In mathematics, a prime power is a positive integer which is a positive integer power of a single prime number.For example:, and are prime powers, while, and are not.
The sequence of prime powers begins:
2, 3, 4, 5, 7, 8, 9, 11, 13, 16, 17, 19, 23, 25, 27, 29, 31, 32, 37, 41, 43, 47, 49, 53, 59, 61, 64, 67, 71, 73, 79, 81, 83, 89, 97, 101, 103, 107, 109, 113, 121, 125, 127, 128, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 243, 251, ….
The prime powers are those positive integers that are divisible by exactly one prime number; in particular, the number 1 is not a prime power. Prime powers are also called primary numbers, as in the primary decomposition.
Prime powers are powers of prime numbers. Every prime power (except powers of 2 greater than 4) has a primitive root; thus the multiplicative group of integers modulo pn (that is, the group of units of the ring Z/pnZ) is cyclic.[1]
The number of elements of a finite field is always a prime power and conversely, every prime power occurs as the number of elements in some finite field (which is unique up to isomorphism).[2]
A property of prime powers used frequently in analytic number theory is that the set of prime powers which are not prime is a small set in the sense that the infinite sum of their reciprocals converges, although the primes are a large set.[3]
The totient function (φ) and sigma functions (σ0) and (σ1) of a prime power are calculated by the formulas
\varphi(pn)=pn-1\varphi(p)=pn-1(p-1)=pn-pn-1=pn\left(1-
| 1 | |
| p |
\right),
| n) | |
| \sigma | |
| 0(p |
=
| n | |
| \sum | |
| j=0 |
p0 ⋅ =
| n | |
| \sum | |
| j=0 |
1=n+1,
| n) | |
| \sigma | |
| 1(p |
=
| n | |
| \sum | |
| j=0 |
p1 ⋅ =
| n | |
| \sum | |
| j=0 |
pj=
| pn+1-1 | |
| p-1 |
.
All prime powers are deficient numbers. A prime power pn is an n-almost prime. It is not known whether a prime power pn can be a member of an amicable pair. If there is such a number, then pn must be greater than 101500 and n must be greater than 1400.